If you are using network address translation with device resolver

The device resolver is not supported if you use network address translation (NAT) to translate an IP address in your local network to a different IP address known within another network. The device resolver is also not supported when translating an IP address to a different IP address or source port number combination.

Using NAS

The network access server (NAS) sends a RADIUS message to the SafeLinx Server each time a mobile client connects to the NAS. The RADIUS message contains the IP address allocated to the mobile device and a unique device identifier, such as a phone number or user ID. On all subsequent requests from the mobile device, the SafeLinx Server uses this information to establish a mapping between the mobile device IP address and the unique identifier.

Using NAT

If a NAT computer exists in the network between the mobile device and the SafeLinx Server, the source IP address is then changed to an address assigned by the NAT computer. Typically, this address reassignment is dynamic, so an individual device might not be assigned the same IP address each time it connects to the network. The problem is that the IP address in the RADIUS message does not match the address assigned by the NAT computer. The NAT computer modifies the source address of the device request and does not generally have awareness of the data that is flowing through it.